Originally Posted by Elli
We cut them at each emergency exit and the doors. Just the wires that made them impossible to remove
Well, hopefully all you need to do to get your bus started at least is to ground the powered wire leading to the barrel lock on your side exit door. The interlock is basically a single circuit that needs to be continuous for the bus to start. When either of the barrel locks on the emergency doors is thrown (meaning the door cannot be opened), this breaks the circuit and the bus can't be started.
If you locate the powered wire leading to the barrel lock on the side, you can strip the end and connect it to the bus body with a sheet metal screw. This will complete the circuit and allow your bus to start (the barrel lock will also have a second wire for ground - if you ground that on instead of the powered wire, the bus still won't start). You could also just splice the two wires (powered and ground) together to complete the circuit.
Note: you want to do this with the wire leading to the side door rather than the back door because the side door is the first one in the circuit (with the wires cut the back door barrel lock is not receiving any juice anyway, so grounding the powered wire won't do anything). You said you also cut wires on your doors (plural), and I'm not sure where they are in this circuit (or if they're even part of the starter interlock at all - I don't think they are).
I bypassed my interlock in this way. I want to keep the circuit active because when I complete my conversion, I'm going to wire it up to cabinet doors and stuff that I want to make sure I remember to close whenever I drive (like a cat door I'm going to put on my exit door).